Transcranial Doppler (TCD) ultrasonography has gained widespread acceptance as a non-invasive method for the evaluation of cerebrovascular physiology such as monitoring of blood flow velocities from any of the vessels accessible through the transtemporal window. A major disadvantage of TCD ultrasonography is that the patients must be cooperative and somewhat still during insonation, in order to assure adequate sampling of Doppler signals. Attempts to carry out such monitoring have met with the obstacle of proper stabilization of the TCD transducer. Even under conditions of relative patient immobility, i.e., during surgical procedures, various investigators have reported difficulties obtaining accurate blood flow velocity measurements. The major problem noted has been probe displacement during continuous monitoring. In an attempt to overcome this, several somewhat cumbersome methods for stabilizing TCD transducer housings have been developed with variable success and their own inherent limitations. There is a need for a simple yet reliable TCD transducer housing stabilizer which is practical and which allows continuous monitoring without regard to patient position or head movement.